Finality

Finality is the moment a block becomes permanent. Before it, a transaction is a claim; after it, the transaction is history that no honest node will roll back. Chains differ in how they reach that point. Probabilistic designs such as proof-of-work only make a block less and less likely to be replaced as more work accumulates on top of it, which is why exchanges and bridges wait for many confirmations. BFT consensus takes the other route: a block signed by a supermajority of known validators is final the instant it is committed, and honest nodes never reorganize it.

Chain 2800 takes the second route. It runs QBFT with nine validators and a quorum of six: once six commit signatures exist for a block, that block is final. Blocks are produced roughly every 500 ms, so inclusion and finality arrive together, in about half a second. The commit signatures are classical ECDSA over secp256k1; chain 2800 does not claim post-quantum consensus.

Two further mechanisms guard finalized history. A second client, an independently implemented Nethermind fork, validates every block alongside the producing client, which is the point of client diversity. And since block 13,014,000, every 32nd block header carries a post-quantum anchor: a certificate of Falcon-512 signatures from the validators over the parent block, at least 3 per anchor block and 5 in practice, whose 32-byte digest sits inside the data covered by the block hash.